Honestly the main reason seems to be that it looks less intimidating. Open vi and no help is offered in terms of commands, it's just an empty screen. Same for Emacs i think. Nano looks like something built for humans.
VIM - Vi IMproved
version 8.2.4133
by Bram Moolenaar et al.
Vim is open source and freely distributable
Help poor children in Uganda!
type :help iccf<Enter> for information
type :q<Enter> to exit
type :help<Enter> or <F1> for on-line help
type :help version8<Enter> for version info
Running in Vi compatible mode
type :set nocp<Enter> for Vim defaults
type :help cp-default<Enter> for info on this
"No help offered" or "just an empty screen" is not how I would describe the above text.[1]: https://github.com/vim/vim/blob/a96edb736d4274fc4aea46080078...
Also I like to use Vim's terminal buffer, and it turns out accidentally starting Vim inside Vim rarely leads to satisfying results.